Police in Myanmar were accused of beating and detaining protesters on Thursday as they broke up the country’s first major demonstrations in years.

The spreading rallies against power cuts, the first protests since a deadly crackdown on monk-led demonstrations in 2007, are being closely watched as a test of the new quasi-civilian government’s tolerance of public discontent.

Several demonstrators were beaten and six people were taken away by police for questioning for several hours, said protest leader Kyaw Swe, one of those detained in Pyay town, some 300 kilometres (180 miles) north of Yangon.

“Two men… were seriously injured as the police beat us while we were protesting. I was also beaten,” he told AFP by telephone after his release.

Myanmar demonstrators light candles and pray during a protest against severe power cuts at Sule pagoda in Yangon. Police in Myanmar were accused of beating and detaining protesters on Thursday as they broke up the country's first major demonstrations in years. (AFP)

“Our whole town is in trouble because of the lack of electricity. That’s why we decided to protest. We are just asking for our rights.”

A local resident also reported heavy-handed tactics.

“About 50 police arrived and asked the people to stop… some people were injured,” Nyi Nyi Aung said.

Nyan Win, a spokesman for opposition leader Aung San Suu Kyi’s National League for Democracy (NLD) party, said three or four of its members were among those detained in Pyay.

The rallies, which started at the weekend in Mandalay, Myanmar’s second-largest city, have also spread to Yangon, where about 250 residents on Wednesday defied a police request to disperse.

Until Thursday’s incident, police had not deployed tough tactics to disperse protests.

Myanmar President Thein Sein, a former general, has won international praise for reforms including releasing hundreds of political prisoners and welcoming Suu Kyi and her party back into mainstream politics.

A police official in Yangon, who did not want to be named, expressed surprise at the beatings, adding there had been no wider order to crack down on the rallies.

“We have no instruction to arrest or beat the protesters. I have no idea why it happened,” he said.

“The local authorities might need to give an explanation to their superiors.”

On Tuesday, about 10 NLD members were held by police for several hours in Mandalay for questioning and later released without charge.

The government directly addressed the protests and power shortage issue on Thursday – a rare recognition of public sentiment in the country formerly known as Burma, where decades of outright military rule ended last year.

“It is usual in a democratic country that people express their desire by protesting. But they need to be lawful,” presidential adviser Ko Ko Hlaing told a press briefing.

“They can protest to the extent that the law permits. According to the law, if they want to protest, they need to inform the police station and get permission.”

The impoverished country suffers crippling power cuts and only 13 percent of the population has access to electricity, according to 2009 figures from the World Bank.

State newspapers have run articles explaining energy policy and the New Light of Myanmar said nearly 40 new generators have been deployed in the three protest cities, while more have been ordered from overseas.

The 2007 monk-led “Saffron Revolution”, which was brutally crushed by the military, began as protests against rising fuel prices.